Method for manufacture of a metal shell, and a cup designed to serve as a blank

ABSTRACT

The invention relates to manufacture of a cup ( 1 ) that is designed to serve as a blank in the production of a metal shell ( 2 ) by providing a body ( 3 ) of a bar material, placing the body ( 3 ) in a counterdie ( 6 ) in which a first end surface of the body ( 3 ), which is substantially perpendicular to the central axis (C) of the body, is placed facing towards the bottom of the counterdie while the inner wall of the counterdie ( 6 ) encloses at least a part of the body and preferably the whole body, so that the body ( 3 ) is hereby placed in the counterdie ( 6 ), applying a mandrel ( 9 ) to a second end surface of the body that is substantially perpendicular to the central axis C of the body ( 3 ), applying a pressing force to the mandrel ( 9 ) so that the body ( 3 ) is cold flow pressed through plastic deformation into a cup ( 1 ). The invention also relates to an application of a body for manufacture of a blank for a grenade/cartridge shell and a process for manufacture of a grenade/cartridge shell.

This application is a 35 USC 371 of PCT/SE03/01156 filed Jul. 3, 2003.

TECHNICAL FIELD

The present invention relates to a method for manufacture of a metalshell in a steel, aluminium or copper alloy. The invention also relatesto a method for manufacture of a cup designed to serve as a blank.

PRIOR ART

Forming of metals can take place both in a warm and a cold state. Thepresent invention relates to forming through a specific method calledcold forging. Cold forging can be divided into three main types, coldflow pressing, deep drawing and upsetting.

Cold forging refers to a method of forming at a temperature that liesbelow the recrystallization temperature of the material. Cold forginghas a number of advantages compared with other methods of forming, someof the advantages being forming of complicated shapes, a reduction inmaterial wastage and good surface smoothness without the need forsubsequent working. Cold forging also offers the opportunity toinfluence the metal's grain structure, size and orientation in a uniqueway. This gives improved electrical and mechanical properties, improvedhardenability and improved hardness through deformation hardening.

For cold working of a metal, it is necessary for it to have specificproperties including good ductility. Carbon steel, low alloy steel,specific aluminium alloys, brass and bronze are metals with theseproperties. Apart from adding various alloying metals to the metal,desirable properties are obtained by transformations of the structure ofthe material due to heat treatment among other things.

An example is given in JP57089466 of how it is said to be possible toachieve good cold working properties by alloying aluminium with 1.0–3.0percent by weight Mn and up to 0.3 percent by weight Fe and directlyfollowing casting into a billet, i.e. a bar of slender dimensions, inthis case with a diameter of 155 mm, quenching the material to therebyobtain magnesium in solid solution in the material. This billet is cutinto pieces, which are then cold flow pressed to the desired shape andit is stated that the product obtained has good strength propertieswithout any heat treatment being required.

The manufacture of metal shells, and in particular of shells for use incartridge production, currently takes place from a blank consisting of around, i.e. a thin circular disk cut out of cold-rolled sheet in asuitable material quality, for example SSEN 6082 (European standard),which is specially alloyed aluminium. Another suitable material can bebrass. The round is shaped in a preliminary production stage by means ofdeep drawing and turning to form a cup that is then washed, annealed andpickled, following which it is worked further including by means offurther deep drawing to give a finished shell. To manufacture cartridgeshells, a round of this kind can have a thickness of around 10 mm and adiameter of approx. 160 mm.

For the round to withstand the load caused by subsequent deep drawing toform a finished shell, the material is required to a have a degree ofreduction of at least 30% from the cold rolling. Cold rolling gives acharacteristic structure of the material consisting of grain stretchedin the direction of rolling, which gives desired strength propertiesthrough deformation hardening.

An example of the prior art for the manufacture of shells is shown inU.S. Pat. No. 2,264,266.

In the manufacture of a shell from this round that is of immediateinterest to the invention, however, the grain structure of the materialbrings the disadvantage that the material flows with varying ease indifferent directions. During deep drawing, the material will move in thedirections in which it flows most easily, i.e. where the resistance todeformation is lowest, and the result is that the material will not bedistributed entirely evenly when the wall is formed. This results in theformation of characteristic so-called drawing lugs in the top edge ofthe cup, for which reason the cup has to be turned so that an even topedge is obtained. The method does not offer any opportunity either toobtain a certain thickness of the cup's bottom and walls in a controlledmanner, resulting in disadvantages in subsequent production stages.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to a method for manufacture of a cup that isdesigned to serve as a blank in the production of a metal shell in analuminium or copper alloy, for example, especially aluminium in a gradetermed SSEN 6082. The invention is particularly well suited to themanufacture of blanks designed to be used in the production of shellswith through holes, for example grenade or cartridge shells. The blankfor the cup is obtained by cutting from a standardized bar material ofsuitable dimensions to give a body of suitable length. The bar materialcan be pressed, drawn or rolled bar with a circular, square,rectangular, hexagonal or other cross-section. To manufacture acartridge shell, a bar with a circular cross-section is best used, sothat a circular-cylindrical body is obtained on cutting. The body ischaracterized in that it is solid and has two end surfaces that aresubstantially parallel to one another and has a substantial extension inall planes, i.e. an extension vertically, laterally and longitudinally.The ratio between the largest and the smallest dimension can lie in thiscase in a range between 1:1–5:1. The body is turned if necessary to theexact diameter. The body is annealed and a lubricant applied, followingwhich the body is cold flow pressed to give a cup.

In cold flow pressing, a surrounding wall is formed that is deformeduniformly, so that the upper open end of the cup acquires asubstantially even edge that does not need to be turned. The cup is thenwashed, annealed again and pickled in order to undergo deep drawing toform a shell in the next production stage. The shell is cut off at thetop edge to the desired length and the bottom flanged to the desiredshape, following which the remaining material in the bottom of the shellis cut out. Finally the shell is solution heat treated, artificiallyaged and turned before it is surface finished and given a finalinspection for delivery to the customer.

Due to the initial cold flow pressing, the bottom thickness of the cupcan easily be varied as it is determined as a function of the quantityof material required for the flanging. When a round is used, the cup'sbottom thickness cannot be varied, as the cup is formed by deep drawingof the round, which deep drawing is not designed to reduce the bottomthickness. On the other hand, it occurs that the bottom thickness isreduced unintentionally owing to the grain structure of the material,which gives rise to disadvantages in production.

It has also proved to be the case that the use of a round results inunnecessary wear on the flanging tools. The wear is caused by theflanging tools having to be compressed more than is desirable as thequantity of material remaining in the bottom of the shell is sometimesvery little. This results in very high temperatures in the remainingmaterial in the bottom of the shell, which increases the wear on thetools.

The reason that there is sometimes too little material is that thecold-rolled material structure in the round does not flow equally easilyin all directions, which is why it is difficult to control thethickness. According to the present invention, the wear on the flangingtools as a result of such overheating can be avoided or minimized byadjusting the bottom thickness of the cup depending on the quantity ofmaterial required for flanging in the preliminary cold flow pressing.

The invention also has cost advantages. By using a bar material that iscut into the correct lengths, the consumption of raw material isminimized in the sense that no wastage or very little wastage occurscompared with manufacturing shells from rounds, in which the rounds arecut out of cold-rolled sheet, resulting in large amounts of waste. Thismeans that the rounds are comparatively expensive to purchase. The factthat the forming of the cup can be done in an ordinary press of astandard type by simply exchanging tools also makes production cheaper.Due to cold flow pressing the cup acquires such material properties aswell as such dimensional accuracy that it can be deep drawn to afinished shell without any intermediate working, which offers costadvantages. The reduced wear on the tools in flanging offers a furthercost advantage.

OBJECT OF THE INVENTION

One object of the invention is to offer a method of manufacture of ametal shell in which the material has improved flow properties in thepreliminary forming of a blank into a cup. Another object of theinvention is to determine the thickness of the cup's bottom and walleasily and also in a more controlled manner. A further object is tooffer a more flexible and cost-effective production process.

DESCRIPTION OF FIGURES

FIG. 1A shows a cross-section of around from a sheet material;

FIG. 1B shows a cross-section of a body from a bar material;

FIG. 2 shows a cross-section of a body that has been turned to size andprovided with a drilled hole in the centre;

FIGS. 3A–3C show diagrammatically cold flow pressing of a body to form acup;

FIG. 3D shows a cross-section of a cup that has been obtained by coldflow pressing of a body;

FIGS. 4A–4B show diagrammatically deep drawing of a cup to form a shell;

FIG. 4C shows a cross-section of a shell directly following deepdrawing;

FIG. 5 shows a cross-section of a shell following cutting to the correctlength;

FIG. 6 shows a cross-section of a shell following flanging of thebottom;

FIG. 7 shows a cross-section of a shell following cutting out of thebottom;

FIG. 8 shows a cross-section of a finished shell following drawing.

DETAILED DESCRIPTION

The invention is to be described in greater detail with reference to theenclosed figures, which show the various manufacturing stages for ashell that constitutes an example of a suitable product according to theinvention and can also be said to show a preferred embodiment Thefinished shell has a diameter of 10–500 mm, preferably 30–350 mm andeven more preferredly 50–200 mm and a height of 50–3000 mm, preferably50–2000 mm and even more preferredly 100–1000 mm, and has a minimum wallthickness in the mouth of the shell of 0.5–3.0 mm, preferably 1.2–2.0 mmand even more preferredly 1.3–1.7 mm. However, the invention is notrestricted to the manufacture of shells but is also suitable for theproduction of other objects that are to be cold flow pressed and deepdrawn, for example cylinders. Depending on the size of the productsmanufactured, the tools and machines are adapted to withstand the loadthat the various production stages entail.

The manufacture of a deep-drawn metal shell 2 takes place today from ablank in the form of a round R from a cold-rolled sheet. The round R isrelatively thin in relation to its diameter. When producing a metalshell according to the invention, one starts instead from a body 3 cutfrom a bar material. The body 3 is cold flow pressed to give a cup 1,which is shaped into a shell 2 by deep drawing and worked further to thedesired shape. The body 3 has a substantial extension in all dimensions.

FIG. 1A shows a cross-section of the round R, which according to amethod currently used in Sweden forms a blank in the manufacture of adeep-drawn metal shell. The round R is in the form of a circular diskthat is cut out of a cold-rolled sheet with a degree of deformation ofat least 30%. The degree of deformation is essential, as it gives thematerial the necessary strength properties to withstand the load thatplastic working brings about during the manufacturing process.

The dimensions of the round R are determined by the quantity of materialrequired for production and it is essential that the round has asuitable thickness which, in the preliminary process stage when theround is formed into a cup by deep drawing, gives the cup its bottomthickness. The round R is provided with a drilled hole 16 in the centreand its edges are deburred, following which it is annealed and pickled.The purpose of the hole 16 is to drain away liquid during pickling.

FIG. 1B shows a side view of a body 3 that forms a blank in themanufacture of a shell according to the invention. The body 3 isobtained by cutting a bar material of a suitable dimension to a suitablelength. The bar material is cut so that the section surfaces 4, 5 of thebody 3 are substantially parallel to one another and substantially atright angles to the central axis C of the bar. If necessary the body 3is turned all round to the exact dimensions. The body 3 has a width ordiameter of 10–500 mm, preferably 30–350 mm and even more preferredly50–200 mm and a height of 5–300 mm, preferably 10–100 and even morepreferredly 20–50 mm. The section surfaces 4, 5 of the body 3 are itsend surfaces and height refers to the distance between its two endsurfaces 4, 5. In a preferred embodiment, the cup 3 iscircular-cylindical but it can also have a different shape, for examplea shape with a square cross-section.

FIG. 2 shows a cross-section of a body 3 that has been turned to theexact dimensions and provided with a hole 17 in the centre, for examplea drilled hole. In this case the hole 17 serves two purposes, on the onehand to drain away the pickling liquid, but also to centre the body 3 ininteraction with a mandrel 9 (see FIG. 3A) during cold flow pressing sothat the quantity of material is distributed symmetrically, which givesbetter accuracy of the wall thickness.

FIGS. 3A–3C show diagrammatically how a cup 1 is obtained by cold flowpressing of a body 3 and FIG. 3D shows a cup 1 obtained by cold flowpressing. Cold flow pressing is a forming method in which the material,in this case an aluminium body 3, is forced to flow out into arestricted space by applying a pressing force to the material. Therestricted space is formed by a counterdie 6, which interacts with amandrel 9 in such a way that a space of the desired shape is formedbetween these two when they are brought together. The space can bewholly or partly delimited by these two tools 6, 9.

The counterdie 6 refers to the forming tool that externally shapes theblank that is to be worked and the mandrel 9 refers to the forming toolused to give a blank an internal shape in various types of cold formingmachines.

In cold flow pressing of a cup 1 according to FIG. 3D for themanufacture of a shell 2 according to the invention, the body 3 can beturned to size if necessary, following which it is provided with a hole17, for example by drilling a hole 17. The hole 17, which is preferablya through hole, is suitably drilled so that it coincides with thecentral axis C of the body 3. The body 3 is then annealed and alubricant applied. With reference to FIG. 3A, the body 3 is shown placedin the counterdie 6, which is done in such a way that a first endsurface 4 of the body 3 that is essentially perpendicular to the centralaxis C of the body 3 is placed facing towards the bottom 7 of thecounterdie 6. The inner wall 8 of the counterdie 6 encloses at least apart of the body 3 and preferably the whole body 3, so that the body 3is hereby placed in the counterdie 6. The mandrel 9 is applied to theend surface 5 of the body 3 lying free. At the front the mandrel 9 isprovided with a guide pin 18, which fits into the hole 17 in the centreof the body 3. The guide pin 18 is preferably placed centrally on themandrel 9 and the guide pin 18 preferably has a cylindricalcross-section. The guide pin 18 interacts with the through hole 17 ofthe body 3 and a hole 19 in the counterdie 6, so that correctpositioning of the body 3 is obtained. This preferably means that thebody 3 is centred. The guide pin can be arranged fixedly or movably tointeract with the mandrel. The guide pin in FIG. 3A is an example of afixed guide pin. A movable guide pin is movable in an axial directioninside the mandrel. The guide pin is suitably arranged so that itscentral axis coincides with the central axis of the mandrel. It ishereby ensured that the quantity of material in the body 3 isdistributed symmetrically around the mandrel 9, which gives advantagesin production. It is perceived that the through hole 17 of the body 3and the hole 19 of the counterdie suitably have a shape and dimensionthat correspond to the shape and dimension of the guide pin 18. Asuitable dimension of the guide pin can be in the range of 5–30 mm. Itis also perceived that the hole 19 in the counterdie is preferablyplaced centrally in the bottom of the counterdie 6. When the hole 17 inthe body 3 coincides with the central axis C of the body and the guidepin 18 of the mandrel 9 is placed centrally on the mandrel, theadvantage is achieved that the mandrel can act symmetrically on the body3, particularly if the hole 19 of the counterdie is placed centrally inthe bottom of the counterdie 6 and the guide pin 18 can also interactwith the hole 19 in the counterdie. This gives a symmetricaldistribution of the quantity of material around the mandrel 9. It is tobe understood that the mandrel 9 preferably has a circular-cylindricalcross-section.

The counterdie 6 surrounds the material both on the underside and to theside and when the mandrel 9 is pressed down in the body 3 the materialwill flow out towards the sides of the body 3 and gradually be forcedupwards into the space formed between the walls 10 and 8 respectively ofthe mandrel 9 and counterdie 6, so that a cup 1 is formed, which isshown in FIG. 3B. The size of the body 3 is adapted so that a sufficientamount of material is available for production but without the quantityof waste being unnecessarily great. During cold flow pressing, thethickness of the bottom of the cup 1 is reduced and the height of thewall of the cup 1 increases as the mandrel 9 acts on the body 3 whenthis lies in the counterdie 6. The cold flow pressing is completed whena predetermined height of the wall of the cup 1 and/or a predeterminedthickness of the bottom of the cup 1 is obtained, see FIG. 3C. Thesedimensions depend on a number of parameters and are decided primarily bythe required quantity of material being present in the bottom and wallof the cup 1 respectively for the manufacture of a shell 2 that is trueto gauge. Another parameter that decides the dimensions of the cup 1 isthat it is desirable to attain a predetermined degree of deformation ofthe finished shell 2. The degree of deformation influences the strengthproperties of the material through deformation hardening and also has aneffect on the hardenability, so that a high degree of deformation givesbetter hardenability. The cold flow pressing operation in which the body3 is formed into a cup by the mandrel 9 and the counterdie 6 can becarried out at room temperature, which contributes to a cost-effectiveprocedure.

The degree of deformation is calculated as the ratio between the totalarea reduction and the original area in a given cross-section. Thedegree of deformation in cold flow pressing, i.e. production stages3A–3C, is calculated as (A1–A2)/A1 where A1 is the cross-sectional areaof the body that is marked in FIG. 3A and A2 is the cross-sectional areaof the cup and is marked in FIG. 3C. The degree of deformation iscalculated in the same way in deep drawing and flanging.

The body 3 has a homogeneous material structure in a direction coaxialwith the central axis C of the body 3 that coincides with the directionof movement of the mandrel 9. In cold flow pressing a circumferentialwall 11 is formed and the homogeneous material structure means that thewall 11 is deformed uniformly, so that an upper open end 12 of the cup 1acquires an essentially even edge 13 due to the cold flow pressing. Thethickness of the wall can also be controlled in a better manner as aresult of the homogeneous material structure. With reference to FIG. 3D,a finished cup 1 is shown in which the circumferential wall 11 formed incold flow pressing in any cross-section perpendicular to the centralaxis C of the cup 1 has an essentially even material thickness d_(v) ina range in which d_(v)=1–50 mm, preferably 2–25 mm and even morepreferredly 3–10 mm and in which the material thickness d_(v) ispermitted a maximum variation of 1.0 mm, preferably a maximum of 0.5 mmand even more preferredly a maximum of 0.05 mm. The bottom 14 of the cup1, formed in cold flow pressing by uniform deformation, has a bottomthickness d_(B) in a range in which d_(B)=1–50 mm, preferably 2–25 mmand even more preferredly 3–10 mm and in which the material thicknessd_(B) is permitted a maximum variation of 1.0 mm, preferably a maximumof 0.5 mm and even more preferredly a maximum of 0.05 mm. Due to thefact that the cup acquires a high dimensional accuracy, no furtherworking needs to be done before the deep drawing, which is a majoradvantage.

FIGS. 4A and 4B show schematically how a shell 2 is obtained by deepdrawing of a cup 1 and FIG. 4C shows a shell 2 directly following deepdrawing. The cold flow pressed cup 1 is washed, annealed and pickled andis thus ready for deep drawing. The deep drawing proceeds such that thecup 1 is placed over a deep drawing counterdie 26, see FIG. 4A, wherethe deep drawing counterdie 26 has the form of rings 27, 28, 29 placedon top of one another, which have a gradually diminishing diameter andin which the smallest diameter corresponds to the outer dimensions ofthe finished shell 2. The cup 1 is placed so that the bottom 14 of thecup 1 is over the opening of the deep drawing counterdie 26 and theupper open end 12 of the cup 1 faces away from the deep drawingcounterdie 26. A mandrel 30 in the form of a rod is guided down into thecup 1 and when it reaches the bottom 14 it pulls the cup 1 down with itthrough the deep drawing counterdie 26, see FIG. 4B, due to which theshell wall is thinned out when it passes the gradually diminishing holesin the deep drawing counterdie 26.

The end of the mandrel 30 that is pressed against the bottom 14 of thecup 1 has a shape that gives the wall 20 of the shell a graduallyincreasing inner diameter from its bottom 21 and upwards in a directionalong the wall 20 of the shell. At a suitable distance from the end, theshape of the mandrel 30 passes over to wholly cylindrical, when thediameter corresponds to the inner diameter of the finished shell. To beable to be guided down into the cup 1, the mandrel 30 has a diameterthat is 0.1–0.5 mm less than the diameter of the cup 1. During deepdrawing the wall will be pressed until it bears on the mandrel 30 due tothe effect of the outer deep drawing counterdie 26. Depending on howgreat a reduction is to be made in the thickness of the wall, the numberof stages by which the diameter of the deep drawing counterdie 26diminishes is varied, so that a large reduction requires more stagesthan a small one. The composition of the material with regard to thestarting blank and its strength properties are also of importance forthe number of stages that are required. In manufacture of a shell 2according to the invention, the homogeneous material structure has apositive effect insofar as the shell wall has the same strength overall.This means that the possibility exists of designing the forming toolswith fewer stages, whereby the tool cost is reduced.

Following deep drawing, the wall 20 of the shell 2 is to be cut off atits open end to the correct length. To do this, the shell 2 is placedover a mandrel 31, according to FIG. 5, in a machine that also executesthe subsequent working processes up to the finished shell.

When the shell wall has been cut off, flanging of the bottom 21 of theshell 2 follows. In the flanging, a counterdie (not shown) is pressedagainst the outside of the bottom 21 of the shell 2 and according to thesame principle as in cold flow pressing, the mandrel 31 interacts withthe counterdie (not shown), the bottom 21 of the shell 2 being formedinto a flange 22 with an appearance according to the cross-section inFIG. 6. Since the bottom thickness d_(B) of the cup 1 can easily bevaried in the initial cold flow pressing, it is easy to adapt thequantity of material to different types of flanges.

According to an aspect of the invention, the bottom thickness d_(B) ofthe cup 1 is to be chosen so that wear on the tools that are used inflanging is prevented or reduced. In one embodiment of the invention,the bottom thickness d_(B) is chosen so that it allows the flanging tobe executed so that a central part A of the bottom 21 of the shell 2acquires a thickness d_(A) in a range in which d_(A)=1 mm–10 mm,preferably 4 mm–6 mm and preferably approx. 5 mm.

Following flanging, cutting out of the remaining material in the centralpart A of the bottom 21 of the shell 2 takes place and then the shell 2is washed. FIG. 7 shows a cross-section of a shell 2 following cuttingof the bottom.

To give the shell 2 the desired strength properties it is solution heattreated and quenched according to methods that are well known to theexpert The shell 2 is given its final form, which is shown in FIG. 8, bya slight drawing of the shell wall. Artificial aging to give the shell 2the desirable strength, turning, surface treatment and final inspectionthen take place, the production process thus being completed.

It is also possible to adapt production so that the shell 2 is given therequired strength properties only by the plastic deformation thatmanufacture causes, so that the subsequent solution heat treatment andrelated artificial aging can be avoided, which offers cost advantagesfor the production process.

The shell 2 can suitably be used as a shell 2 in the production ofammunition, i.e. grenade shells or cartridge shells and thus highdemands are made on the strength of the shell to ensure the function ofthe shell. A shell manufactured according to the invention has proved tomeet these requirements well.

With production according to the invention, production advantages can beobtained. Due to the fact that the mandrel for cold flow pressing isprovided with a guide pin 18, a cup 1 can be manufactured that has suchdimensional accuracy that no further working is required prior to deepdrawing, which also offers cost advantages. In this connection, it isimportant that the guide pin 18 has such strength that it providessteady guidance. The guide pin 18 cannot therefore be made too small, asit would result in a risk of it bending, with uneven materialdistribution and poor dimensional accuracy as a result. To obtainsufficient strength, a guide pin 18 designed to be used for manufactureof a shell 2 according to the invention can suitably have a diameter inthe range 5–30 mm, preferably 10–30 mm. The expert perceives that themethod according to the invention is therefore designed primarily formanufacture of shells with through holes.

As described earlier, the cup 3 is given favourable material propertiesdue to the plastic deformation that cold flow pressing gives rise to.This brings with it the advantage that the later deep drawing from cup 1to shell 2 can be executed in a single stage. This preferably means thatthe shell is drawn to its finished length in a single stage. This givesfurther cost advantages.

As stated earlier, the body 3 can undergo a turning operation followingcutting from a bar in order to adjust the diameter of the body 3 to thecounterdie 6. However, no machining other than that required to adaptthe diameter needs to be carried out. As stated earlier, it is howeververy advantageous to drill a through hole 17 through the body 3. Oncutting the body 3 from a bar, the height of the body 3 is suitablyselected so that the height of the body is adapted to the counterdie 6already on cutting from the bar. However, further plastic working shouldpreferably be avoided, since such working could affect the homogeneousmaterial structure around the central axis C of the body 3.

It is perceived that the invention also relates to equipment formanufacture of a shell 2, which equipment comprises a counterdie 6 suchas described above and a mandrel 9 with guide pin 18 such as describedabove. The equipment according to the invention also comprises a furthercounterdie 26 for deep drawing as described above, in which the deepdrawing counterdie 26 takes the form of rings 27, 28, 29 placed on topof one another, which have a gradually diminishing diameter and in whichthe smallest diameter corresponds to the outer dimensions of thefinished shell 2. The equipment according to the invention alsocomprises a mandrel 30 in the form of a rod designed to interact withthe deep drawing counterdie 26 in that the mandrel 30 is guided downinto the cup 1 and pulls the cup 1 down with it through the deep drawingcounterdie 26, due to which the wall 20 of the shell is thinned out whenit passes the gradually diminishing holes in the deep drawing counterdie26. The equipment according to the invention can also comprise means forcutting a bar, for example a metal saw or other cutting device.Furthermore, the equipment according to the invention can comprise meansfor annealing and pickling as well as means for cutting the shell walland means for flanging.

ADVANTAGES OF THE INVENTION

Manufacture of shells according to the invention results in a number ofadvantages, several of which are evident from the description of thefigures. In addition to these already stated advantages, the inventionalso results in the following advantages:

By using a bar material that is cut into the correct lengths, theconsumption of raw materials is minimized in the sense that no wastageor very little wastage arises compared with manufacturing shells fromrounds, where the rounds are cut from cold-rolled sheet, which resultsin large amounts of waste. This means that the rounds are relativelyexpensive to purchase.

Manufacture from a round also requires the cup to be turned at its upperedge, which is not required with manufacture according to the invention,which further reduces wastage.

From the production engineering aspect, it is of course also anadvantage if wastage is minimized when producing the raw material, asotherwise large amounts of material are handled and workedunnecessarily, with the energy consumption and environmental pollutionthis entails.

The homogeneous material structure in the body means that the materialflows more uniformly in all directions and a more controlled cupformation is thereby obtained than when a round is used. Due to this,the cup can be manufactured with greater precision of the wall andbottom thickness.

A substantial advantage of the invention is that the bottom thicknesscan easily be varied. By pressing the mandrel down to a certain depth inthe body, a predetermined thickness of the bottom of the cup isobtained. Thus, the thickness is adjusted depending on the quantity ofmaterial required for flanging. By adjusting the thickness it ispossible to avoid overheating and related wear of the flanging tools asa result of a bottom that is too thin, which is not possible inmanufacture from a round.

The expert perceives that with a variable body according to theinvention, shells and cylinders can be manufactured with greatflexibility as far as the form of the finished product is concerned. Itis possible for example to produce open, closed or partly open bottomsections. With cold flow pressing the bottom can be formed with partsprojecting in the pressing direction in a number of different shapes,for example cooling flanges, rods and other forms that can then beworked further into, for example, eyes, fastening devices or otherthings. The shape of the shell wall can also be varied. The outer sheathsurface of the wall can be circular or cornered, while the inner canhave a completely different shape. A variable body also offers greatflexibility during the actual production process, where the finalproduct can be given desirable properties, e.g. desirable strengthproperties through deformation hardening and desirable hardenabilitythrough a degree of reduction.

The homogeneous material structure also gives the advantage that the cupacquires an essentially even upper edge on cold flow pressing and noturning of the edge is therefore required, which is a must whenmanufacturing from rounds.

Due in particular to the fact that cold flow pressing of a cup from abar material is combined with subsequent deep drawing from a cup to ashell, an efficient procedure is obtained for manufacturing shells.

1. Method for manufacture of a cup that is designed to serve as a blankin the production of a metal shell, which method comprises the followingstages: a) providing a body of a bar material having a through hole; b)placing the body in a counterdie so that a first end surface of the bodythat is substantially perpendicular to the central axis of the body isplaced facing towards a bottom of the counterdie while the inner wall ofthe counterdie encloses at least a part of the body, so that the body ishereby placed in the counterdie, the counterdie having a hole in thebottom; c) applying a mandrel to a second end surface of the body thatis substantially perpendicular to the central axis of the body, in whichthe mandrel has a centrally placed guide pin for interacting with thethrough hole of the body and for interacting with the hole in the bottomof the counterdie so that the body is thereby centered in relation tothe mandrel and in relation to the counterdie; d) application of apressing force to the mandrel, so that the body is cold flow pressedinto a cup by plastic deformation, wherein the hole of the counterdiehas a shape and dimension that corresponds to a shape and dimension ofthe guide pin such that the bar material is prevented from flowingbetween the guide pin and the hole in the counterdie during theapplication of pressing force to the mandrel.
 2. Method according toclaim 1, wherein the body has a width or diameter of 10–500 mm and has aheight of 5–300 mm.
 3. Method according to claim 1, wherein the body hasa width or diameter of 30–350 mm and a height of 10–100 mm.
 4. Methodaccording to claim 1, wherein the body has a width or diameter of 50–200mm and a height of 20–50 mm.
 5. Method for manufacture according toclaim 1, wherein the body forms a part of a bar and has a chieflyhomogeneous material structure around the central axis of the barmaterial.
 6. Method according to claim 1, wherein the cold flow pressinga surrounding wall is formed that is deformed uniformly, so that anupper open end of the cup acquires a substantially even edge due to thecold flow pressing and that the surrounding wall formed in cold flowpressing in any cross-section perpendicular to the central axis of thecup has a substantially even material thickness dV in a range in whichdV=1–50 mm and in which the material thickness is permitted a maximumvariation of 1.0 mm.
 7. Method according to claim 6, wherein the dV=2–25mm.
 8. Method according to claim 6, wherein the dV=3–10 mm.
 9. Methodaccording to claim 6, wherein the material thickness is permitted amaximum variation of 0.5 mm.
 10. Method according to claim 6, whereinthe material thickness is permitted a maximum variation of 0.05 mm. 11.Method according to claim 6, wherein the inner wall of the counterdieencloses the whole body.
 12. Method according to claim 1, wherein thecold flow pressing a bottom is formed that is deformed uniformly inwhich the bottom thickness dB=1–50 mm and in which the materialthickness is permitted a maximum variation of 1.0 mm.
 13. Methodaccording to claim 12, wherein the dB=2–25 mm.
 14. Method according toclaim 12, wherein the dB=3–10 mm.
 15. Method according to claim 12,wherein the material thickness is permitted a maximum variation of 0.5mm.
 16. Method according to claim 12, wherein the material thickness ispermitted a maximum variation of 0.05 mm.
 17. Method according to claim12, wherein a central part of the bottom of the shell following flanginghas a thickness in the range 1 mm–10mm.
 18. Method according to claim 1,wherein said shell is a cartridge shell in which the cartridge shell hasa diameter of 10–500 mm and a height of 20–3000 mm and has a minimumwall thickness at the mouth of the shell of 0.5–3.0 mm.
 19. Methodaccording to claim 18, wherein the cartridge shell has a diameter of30–350 mm and a height of 50–2000 mm and has a minimum wall thickness atthe mouth of the shell of 1.2–2.0 mm.
 20. Method according to claim 18,wherein the cartridge shell has a diameter of 50–200 mm and a height of100–1000 mm and has a minimum wall thickness at the mouth of the shellof 1.3–1.7 mm.
 21. Process for manufacture of a shell, which processcomprises the following stages: a) providing a circular-cylindrical bodyof a bar material; b) forming a through hole in the body, which holecoincides with a central axis of the body; c) placing the body in acounterdie so that a first end surface of the body that is substantiallyperpendicular to the central axis of the body is turned towards a bottomof the counterdie while the inner wall of the counterdie encloses atleast a part of the body so that the body is hereby placed in thecounterdie, the counterdie having a centrally located hole in thebottom; d) applying a mandrel to a second end surface of the body thatis substantially perpendicular to the central axis of the body, in whichthe mandrel has a centrally placed guide pin for interacting with thethrough hole of the body and the hole in the bottom of the counterdie sothat the body is thereby centered in relation to the mandrel and thecounterdie; e) applying a pressing force to the mandrel, so that thebody is cold flow pressed into a cup by plastic deformation, wherein thehole of the counterdie has a shape and dimension that corresponds to ashape and dimension of the guide pin such that the bar material isprevented from flowing between the guide pin and hole in the counterdieduring the application of pressing force to the mandrel; and f) deepdrawing of the cup thus produced so that a shell is formed.
 22. Processaccording to claim 21, wherein the cold flow pressing is terminated whenthe bottom of the cup has acquired a predetermined thickness in therange 3 mm–10 mm.
 23. Process according to claim 21, wherein the shellcomprises a grenade shell.
 24. Process according to claim 21, whereinthe shell comprises a cartridge shell.
 25. Process according to claim21, wherein the through hole is formed by drilling.